Recalibrating Time: When Did I Do that?

A recent study has shown that illusory inversion of temporal order can be induced by the 'intentional binding' of an action with its consequence, and that this is associated with increased activation in a brain area implicated in conflict monitoring.     

What Do Mexican Fruit Flies Learn When They Experience Fruit?

Mexican fruit flies learn fruit characteristics that enable them to distinguish familiar fruits from novel fruits. We investigated whether mature Mexican fruit flies learn fruit color, size or odor. We found no evidence that female flies learn fruit color or size after experience with host fruit, including oviposition. However, green fruit and fruit models were more attractive than yellow and red fruit and fruit models regardless of previous experience. Females with grapefruit experience were more attracted to fruit models with extract of either grapefruit peel or pulp, than to models without extract. Females with no experience with grapefruit were not attracted to models treated with grapefruit extract. These results indicate that females learned fruit odor during exposure to grapefruit.     

Replacing Sources with Sinks: When Do Populations Go Down the Drain?

We investigate the scenario in which some amount of higher quality habitat is destroyed and is then replaced by some undetermined amount of lower quality habitat. We examined how much low‐quality habitat would need to be created to maintain the equilibrium population abundance in the entire geographic area. Using a source–sink model, we find that (1) the number of hectares of created habitat per hectare of destroyed habitat must equal the ratio of the high‐quality habitat's productivity to the low‐quality habitat's productivity, however, (2) if the created habitat is a sink, then there is a threshold fraction of destroyed high‐quality habitat below which the initial population abundance cannot be maintained through the creation of habitat. We illustrate these results using data on Red‐winged Blackbirds (Agelaius phoeniceus) in two different regions where high‐quality habitat is being replaced by or converted into lower quality habitat.     

Do Pheromone Binding Proteins Converge in Amino Acid Sequence When Pheromones Converge?

Convergence in amino acid sequences between proteins can be strong evidence for selection. Here, I look for evidence of convergence in the amino acid sequences of pheromone binding protein (PBP) in response to convergence in pheromones. PBPs are involved in sex pheromone reception by the antennae of male moths. In this role PBPs may selectively bind pheromone components and experience convergent selection in response to convergence in pheromone components. However, examination of the PBPs of the taxa that have converged upon the use of (E)- or (Z)-11-tetradecenyl acetate as their major pheromone component reveals little evidence for convergence in the PBPs identified from these taxa. A few sites show a pattern consistent with convergence or parallelism; however, it cannot be ruled out that these sites share the ancestral state. Two of these sites fall within the proposed binding region of PBPs. These results suggest that PBPs either have not converged in sequence or have converged at very few sites in response to convergence on the same pheromone component. Received: 29 July 1999 / Accepted: 8 November 1999     

When a Duck Initiates Movement,Do Others Follow? Testing Preference in Groups

Choice tests have been widely used to assess animal preferences. In the case of group‐living species, these tests are commonly presented to animals in groups, because isolation can have strong effects on behaviour and motivation. However, assessing preference at the group level could be misleading if strong control of movement, through influential individuals, and group cohesion were present. The needs of majority of the population might not be properly represented by the test results. The current study investigated whether or not groups of ducks (four ducklings per group) have individuals that consistently initiate movement and considered the implications for group cohesion, synchronisation and a measure of preference during a choice test. In all groups included in the analyses, there were ducks that initiated more movements than the rest, and this trend was stronger when leading towards areas providing resources such as pools. Also, more ducks preferentially followed the first initiator (birds initiating most movements within a group) into the bathing area. Group cohesion was higher in groups that frequently had the same individual initiating movement. The number of followers following the ducks that initiated most movements was associated with the measure of preference (time spent at preferred area, as a proportion of total time spent at any area) but the number of movements initiated by these individuals was not. These results highlight the need to consider the effects of initiators and group‐cohesive forces when conducting choice tests in groups of animals.     

Where Do Neurologists Look When Viewing Brain CT Images? An Eye-Tracking Study Involving Stroke Cases

The aim of this study was to investigate where neurologists look when they view brain computed tomography (CT) images and to evaluate how they deploy their visual attention by comparing their gaze distribution with saliency maps. Brain CT images showing cerebrovascular accidents were presented to 12 neurologists and 12 control subjects. The subjects' ocular fixation positions were recorded using an eye-tracking device (Eyelink 1000). Heat maps were created based on the eye-fixation patterns of each group and compared between the two groups. The heat maps revealed that the areas on which control subjects frequently fixated often coincided with areas identified as outstanding in saliency maps, while the areas on which neurologists frequently fixated often did not. Dwell time in regions of interest (ROI) was likewise compared between the two groups, revealing that, although dwell time on large lesions was not different between the two groups, dwell time in clinically important areas with low salience was longer in neurologists than in controls. Therefore it appears that neurologists intentionally scan clinically important areas when reading brain CT images showing cerebrovascular accidents. Both neurologists and control subjects used the "bottom-up salience" form of visual attention, although the neurologists more effectively used the "top-down instruction" form.     

Where,When and Why Do Tsetse Contact Humans? Answers from Studies in a National Park of Zimbabwe

Background

Sleeping sickness, also called human African trypanosomiasis, is transmitted by the tsetse, a blood-sucking fly confined to sub-Saharan Africa. The form of the disease in West and Central Africa is carried mainly by species of tsetse that inhabit riverine woodland and feed avidly on humans. In contrast, the vectors for the East and Southern African form of the disease are usually savannah species that feed mostly on wild and domestic animals and bite humans infrequently, mainly because the odours produced by humans can be repellent. Hence, it takes a long time to catch many savannah tsetse from people, which in turn means that studies of the nature of contact between savannah tsetse and humans, and the ways of minimizing it, have been largely neglected.

Methodology/Principal Findings

The savannah tsetse, Glossina morsitans morsitans and G. pallidipes, were caught from men in the Mana Pools National park of Zimbabwe. Mostly the catch consisted of young G. m. morsitans, with little food reserve. Catches were increased by 4–8 times if the men were walking, not stationary, and increased about ten times more if they rode on a truck at 10 km/h. Catches were unaffected if the men used deodorant or were baited with artificial ox odour, but declined by about 95% if the men were with an ox. Surprisingly, men pursuing their normal daily activities were bitten about as much when in or near buildings as when in woodland. Catches from oxen and a standard ox-like trap were poor indices of the number and physiological state of tsetse attacking men.

Conclusion/Significance

The search for new strategies to minimize the contact between humans and savannah tsetse should focus on that occurring in buildings and vehicles. There is a need to design a man-like trap to help to provide an index of sleeping sickness risk.     

When Do Latent Class Models Overstate Accuracy for Diagnostic and Other Classifiers in the Absence of a Gold Standard?

Latent class models are increasingly used to assess the accuracy of medical diagnostic tests and other classifications when no gold standard is available and the true state is unknown. When the latent class is treated as the true class, the latent class models provide measures of components of accuracy including specificity and sensitivity and their complements, type I and type II error rates. The error rates according to the latent class model differ from the true error rates, however, and empirical comparisons with a gold standard suggest the true error rates often are larger. We investigate conditions under which the true type I and type II error rates are larger than those provided by the latent class models. Results from Uebersax (1988, Psychological Bulletin 104, 405-416) are extended to accommodate random effects and covariates affecting the responses. The results are important for interpreting the results of latent class analyses. An error decomposition is presented that incorporates an error component from invalidity of the latent class model.     

What Do Physicians Know About Normal Pressure Hydrocephalus and When Did They Know It? A Survey of 284 Physicians

Normal pressure hydrocephalus (NPH) is a relatively new neurologic disorder first described by Salamon Hakim of Bogotá, Colombia, in 1965. NPH is characterized by three symptoms — impaired gait, incontinence and dementia — and an anatomic abnormality, i.e., enlargement of the cerebral ventricles, which can be seen on computerized tomographic or magnetic resonance imaging. Surprisingly, the intracranial pressure is normal.     

Do Yellow‐Bellied Marmots Perceive Enhanced Predation Risk When they are Farther from safety? An experimental study

Whereas there are many studies of the time allocated to antipredator vigilance while animals forage, the vast majority of these studies remain correlative. This is potentially problematic because a variety of factors other than variation in perceived risk might influence putative antipredator behaviors such as time allocated to vigilance and foraging. We conducted an experimental study of yellow‐bellied marmot (Marmota flaviventris) antipredator behavior while marmots foraged at a replicated set of feeding stations established 1, 5, 10, and 20 m from their main burrows. Marmots appeared to perceive a reduced risk of predation when they foraged in the presence of other marmots; they allocated more time to foraging and decreased the time allocated to vigilance. When they foraged farther from their burrows, marmots initiated foraging after a substantially greater amount of time, tended to increase the frequency of their bouts of vigilance, and decreased the duration of each bout. Yearling marmots took less time to begin foraging than adults. Marmot flight initiation distance at our feeding trays was independent of the distance they foraged away from the burrow. Taken together, these experimental results demonstrate that marmots' perceptions of risk increased with distance to the burrow and decreased when other individuals were within 10 m of them while they foraged.     

When Do Allocations and Constructs Respect Material,Energy, Financial,and Production Balances in LCA and EEIO?

Conservation of mass and energy are essential to physical accounting, just as price and market balances are essential to economic accounting. These principles guide data collection and inventory compilation in industrial ecology. The resulting balanced surveys, however, can rarely be used directly for life cycle assessment (LCA) or environmentally extended input‐output (EEIO) analysis; some modeling is necessary to recast coproductions by multifunctional activities as monofunctional unit processes (a.k.a. Leontief production functions or technical “recipes”). This modeling is done with allocations in LCA and constructs in input‐output. In this article, we ask how these models respect or perturb the balances of the original inventory. Which allocations or constructs, applied to what type of data set, have the potential to simultaneously respect its multiple physical, financial, and market balances? Our analysis builds upon the recent harmonization of allocations and constructs and the ongoing development of multilayered supply and use inventory tables. We derive the necessary and sufficient conditions for balanced models, investigate the role of data aggregation, and clarify these models' relation to system expansion. We find that none of the modeling families in LCA and EEIO are balanced in general, but special data characteristics can allow for the respect of multiple balances. An analysis of these special cases allows for clear guidance for data compilation and methods integration.     

When Do Short-Wave Cones Signal Blue or Red? A Solution Introducing the Concept of Primary and Secondary Cone Outputs

A recent paper by Oh and Sakata investigates the “incompletely solved mystery” of how the three cone responses map onto perceived hue, and particularly the S cone’s well-known problematic contribution to blueness and redness. Citing previous workers, they argue the twentieth century traditional multistage model does not satisfactorily account for color appearance. In their experiment, increasing S cone excitation with shortening wavelength from about 480–460 nm increased perceived blueness up to the unique Blue point at 470 nm, when (a) it began decreasing and (b) redness perception began increasing. The authors asked, What mechanism can be responsible for such functions? I demonstrate a solution. First, it is shown the problem does not lie in the traditional opponent color chromatic responses yellow-blue, red-green (y-b, r-g, which accurately predict the above functions), but in the traditional multistage model of mapping cone responses to chromatic response functions. Arguably, this is due to the S cone’s hypothetically signaling both blueness and redness by the same mechanism rather than by different, independent, mechanisms. Hence a new distinction or mechanism is proposed for a more accurate model, that introduces the new terms primary and secondary cone outputs. However, this distinction requires that the cones S, M, L each directly produce one of the three spectral chromatic responses b, g, y. Such a model was recently published, based on extremely high correlation of SML cone responsivities with the three spectral (bgy) chromatic responses. This model encodes the former directly onto the latter one-to-one as cone primary outputs, whilst S and L cones have a further or secondary function where each produces one of the two spectral lobes of r chromatic response. The proposed distinction between primary and secondary cone outputs is a new concept and useful tool in detailing cone outputs to chromatic channels, and provides a solution to the above “incompletely solved mystery.” Thus the S cone has a primary output producing the total b chromatic response and a secondary output that shares with the L cone the production of r chromatic response, thus aligning with Oh and Sokata’s results. The model similarly maps L cone to yellowness as primary output and to redness as secondary output.     

When Is Visual Information Used to Control Locomotion When Descending a Kerb?

Background

Descending kerbs during locomotion involves the regulation of appropriate foot placement before the kerb-edge and foot clearance over it. It also involves the modulation of gait output to ensure the body-mass is safely and smoothly lowered to the new level. Previous research has shown that vision is used in such adaptive gait tasks for feedforward planning, with vision from the lower visual field (lvf) used for online updating. The present study determined when lvf information is used to control/update locomotion when stepping from a kerb.

Methodology/Principal Findings

12 young adults stepped down a kerb during ongoing gait. Force sensitive resistors (attached to participants'' feet) interfaced with an high-speed PDLC ‘smart glass’ sheet, allowed the lvf to be unpredictably occluded at either heel-contact of the penultimate or final step before the kerb-edge up to contact with the lower level. Analysis focussed on determining changes in foot placement distance before the kerb-edge, clearance over it, and in kinematic measures of the step down. Lvf occlusion from the instant of final step contact had no significant effect on any dependant variable (p>0.09). Occlusion of the lvf from the instant of penultimate step contact had a significant effect on foot clearance and on several kinematic measures, with findings consistent with participants becoming uncertain regarding relative horizontal location of the kerb-edge.

Conclusion/Significance

These findings suggest concurrent feedback of the lower limb, kerb-edge, and/or floor area immediately in front/below the kerb is not used when stepping from a kerb during ongoing gait. Instead heel-clearance and pre-landing-kinematic parameters are determined/planned using lvf information acquired in the penultimate step during the approach to the kerb-edge, with information related to foot placement before the kerb-edge being the most salient.     

Do Males and Females of the Two-Spot Ladybird, Adalia bipunctata (L.), Differ in When They Mature Sexually?

After emergence from pupae males and females of Adalia bipunctata reared under the same constant conditions showed similar refractory periods in their mating behavior. The statistically significant slight protogyny might indicate that it is advantageous for females to accept mating and store sperm for a short period prior to becoming sexually mature, whereas males need to become sexually mature in order to mate. As the two-spot ladybird has overlapping generations, theory predicts that the most effective strategy for both sexes is to have similar sexual maturation periods. The results of this study support this prediction. The actual lengths of the maturation periods, however, will depend largely on the prevailing temperatures and the quality and quantity of food available to the beetle.     

Empathy and Effortful Control Effects on Early Adolescents’ Aggression: When Do Students’ Perceptions of Their School Climate Matter?

Guided by the social emotional learning framework, this study examined whether early adolescents’ social awareness (empathic concern, perspective taking) and self-management (effortful control) would uniquely contribute to early adolescents’ subsequent forms of aggression, and whether perceptions of their school climate (friction, cohesion, competition, satisfaction with classes) would moderate those associations. Participants were 479 10- to 14-year old students (54% female; 78% European American) who completed the first wave of a survey in sixth and seventh grades and the second wave 1 year later. Hierarchical regression analyses indicated that across gender, empathic concern was the only competency to reduce subsequent overt and relational aggression. None of the school climate perceptions made unique contributions to aggression, nor did they show protective functions. Rather, several instances of cumulative advantage were observed, whereby positive school climate perceptions only reduced aggression for students with high levels of empathic concern. Unexpectedly, boys’ perceived cohesion contributed to overt aggression if they reported high levels of effortful control.